Hurricane Isaias Is Moving Through the Bahamas and Will Track Near Florida, East Coast Into Next Week - The Weather Channel

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• Hurricane conditions are expected over portions of the Bahamas Friday.
• Isaias has prompted tropical storm watches in Florida.
• First impacts could be felt in parts of Florida as soon as Saturday.
• The forecast for this system is still uncertain because of multiple factors.
• Isaias may ultimately impact a sizable swath of the East Coast as far north as New England early next week.

Hurricane Isaias (ees-ah-EE-ahs) will track through the Bahamas into Saturday and near Florida this weekend, before tracking up the East Coast as far north as New England next week.

Isaias became a hurricane following an investigative flight by the Hurricane Hunters late Thursday, which found winds of 80 mph. Isaias remains a Category 1 hurricane, on the Saffir-Simpson Hurricane Wind Scale.

(MORE: Hurricane Season Terms You Need to Know)

Tropical storm watches are in effect for parts of the Florida Peninsula, including Miami, Fort Lauderdale and West Palm Beach. A watch means tropical storm conditions are possible Saturday and Saturday night.

Hurricane warnings have been issued for the Bahamas, including Nassau, Freeport and the Abacos Islands, where hurricane conditions are expected into Saturday.

Tropical storm warnings remain in effect from the Dominican Republic and Haiti. A warning means tropical storm conditions are either expected or are already occurring.

Watches and Warnings

(A watch is issued when tropical storm or hurricane conditions are possible within 48 hours. A warning is issued when those conditions are expected within 36 hours.)

Strong winds and bands of rain are spreading into the southeast Bahamas. Wind gusts over 50 mph have been measured in the Turks and Caicos late Thursday night.

Bands of heavy rain are persisting in parts of Hispaniola, particularly over the Dominican Republic.

Heavy rain triggered serious flash flooding in several areas of Puerto Rico. Just under 4.5 inches of rainfall was measured in San Juan on Thursday. Multiple fallen trees, mudslides and flooding was reported in southwest Puerto Rico, according to local emergency management. River flooding has been recorded by USGS gauges in several locations in Puerto Rico.

(NEWS: Isaias Triggers Flooding, Knocks Out Power in Puerto Rico)

Below is a look at what we know about the forecast for any potential U.S. and Caribbean impacts.

Florida, East Coast U.S. Concern

The NHC projected path below shows that this system could be located near or east of the Florida Peninsula by this weekend. Isaias will then gradually move northeastward near the East Coast. However, this forecast is not nearly as straightforward as it might seem.

Current Information and Projected Path

(The red-shaded area denotes the potential path of the center of the system. It's important to note that impacts (particularly heavy rain, high surf, coastal flooding, winds) with any tropical cyclone usually spread beyond its forecast path.)

There are a number of reasons for this uncertainty in both track and intensity.

It's still too early to precisely determine this system's future track and intensity, with regard to the mainland U.S. and, therefore, potential impacts including rain, wind, and storm surge flooding.

Here is what we are actively figuring out right now:

Intensity Considerations

Despite Isaias' recent upgrade, the hurricane is forecast to battle somewhat unfavorable upper-level winds - producing what meteorologists refer to as wind shear - along its track from the Bahamas and beyond. This is usually a nemesis of tropical cyclones.

Current Satellite, Wind Shear Analysis

(Areas of clouds are shown in white. Areas of strong wind shear, the difference in wind speed and direction with height, are shown in purple. High wind shear is hostile to mature tropical cyclones and those trying to develop.)

However, warm water is plentiful near the Bahamas and the Southeast U.S. coast, a factor that would favor intensification.

These sum of these two competing factors should lean toward slow intensification as shown in the National Hurricane Center forecast.

Track Considerations

The forecast track going forward leans heavily on steering features in the atmosphere – the Bermuda high and an upper-level dip in the wind flow over the Mississippi Valley. How strong Isaias is early next week also plays a role in its track.

There are also large uncertainties in how fast Isaias moves near the East Coast. Some computer model forecasts are faster, some a bit slower. So, the timing of all this may also change.

Isaias is expected to make a northward, then northeastward turn this weekend into early next week. But exactly when and how sharp that turn occurs will heavily influence impacts in Florida and along the East Coast. And that depends on the exact orientation and strength of those steering features.

The National Weather Service will be releasing extra weather balloons to help figure out these atmospheric steering agents in the next few days.

Steering Factors in Play

(The Bermuda high and an upper-level trough over the Mississippi Valley may help guide the system in the Southeast U.S., assuming it survives until then. The potential forecast path from the National Hurricane Center is shown in red. )

In general, there are three potential track scenarios regarding the East Coast this weekend into next week:

1. The storm turns sharper, sooner and remains far enough offshore to only bring glancing rain and wind to Florida and parts of the East Coast.

2. The storm turns less sharp and later, moving into the Florida Peninsula, then largely inland with soaking rain along its path.

3. A path generally between the first two described above, where the storm rides up the East Coast with rain, wind, some surge flooding from Florida's east coast perhaps as far north as the Northeast Seaboard.

For now, this third scenario appears to be favored by most computer forecast models, but that could change.

Isaias is expected to arrive near South Florida Saturday as a hurricane, and possibly central or northeast Florida late Saturday and Sunday. That would result in at least some rain, wind, high surf, and coastal flood or storm surge impacts in Florida this weekend.

Chance of Tropical Storm Force Winds and Most Likely Arrival Times

(The contours above show the chance of tropical-storm-force winds (at least 39 mph), according to the latest forecast by the National Hurricane Center.)

From there it could pass near the Carolinas Monday, then sweep quickly near parts of the Northeast Seaboard as far north as New England Tuesday or Wednesday.

Swells generated by Isaias could begin arriving along the Southeast coast of the U.S. as soon as early Saturday, leading to high surf and the danger of rip currents. Surf will remain elevated through the duration until Isaias passes.

Residents along the East Coast from Florida to Maine should monitor the progress of this system closely and have their plans ready to go, in case they're needed.

Caribbean, Bahamas Forecast

As mentioned earlier, Isaias is producing strong wind gusts and bands of heavy rain over Hispaniola, the Turks and Caicos and the southern Bahamas.

Current Wind Field

(The orange circle shows the extent of the system's tropical-storm-force winds (at least 39 mph). The purple circle indicates the extent of hurricane-force winds (at least 74 mph), according to the National Hurricane Center.)

For the Dominican Republic and Haiti, conditions should gradually improve Friday morning. Dangerous flash flooding and mudslides are expected, particularly in the higher terrain of these areas, where up to 12 inches of rain could fall.

Rainfall of 4 to 8 inches is likely in parts o the Bahamas, Turks and Caicos, with up to 4 inches in portions of Cuba.

Two to four inches of rainfall is possible from southern Florida into east-central Florida Friday night through Monday, with isolated maximum totals of 6 inches, according to the National Hurricane Center.

Rainfall Forecast

(This should be interpreted as a broad outlook of where the heaviest rain may fall and may shift based on the forecast path of the tropical cyclone. Higher amounts may occur where bands of rain stall over a period of a few hours. )

In the central and northwest Bahamas, conditions will deteriorate Friday, and hurricane conditions are possible Friday night into Saturday, with damaging winds, heavy rain and storm surge flooding.

This includes areas ravaged last September by Hurricane Dorian.

A dangerous storm surge of up to 3 to 5 feet, above ground level, is forecast from the National Hurricane Center, in areas where winds will blow onshore in the Bahamas.

Check back with us at weather.com for important updates on Isaias.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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